1. Field of the Disclosure
The present disclosure relates to a method of manufacturing a sheet metal frame to be used for an electronic apparatus such as an image forming apparatus, and more particularly, to an improvement in surface accuracy and strength of a sheet metal frame.
2. Description of Related Art
Conventionally, a sheet metal frame has been widely used as a frame that constructs a casing of an electronic apparatus, or as a frame for supporting electronic components arranged inside the casing. The sheet metal frame has excellent rigidity, but as a sheet metal becomes thicker, the electronic apparatus becomes heavier, which raises a problem of a cost disadvantage.
Therefore, there is employed a method of forming a drawn portion in the sheet metal frame so as to increase the rigidity while reducing the thickness of the sheet metal frame as small as possible. For example, there is known an electronic apparatus frame having two drawn portions provided across a stay portion, to thereby increase the rigidity and strength of the frame and also enhance an anti-shock characteristic thereof. Further, there is known a structure in which an embossed portion (drawn portion) is provided in at least part of a frame of an image reading section mounted on an image forming apparatus.
By the way, in the case of forming a drawn portion in a sheet metal member as described above, there is a problem in that the sheet metal member is distorted to result in a decrease in surface accuracy. Specifically, when a drawn portion 102 is formed in a sheet metal frame 101 as illustrated in FIG. 6, a material of a corner portion 102a situated on a recessed surface side of the drawn portion 102 is stretched and a material of a corner portion 102b situated on a projecting surface side of the drawn portion 102 is compressed. As a result, the cross section of the sheet metal frame 101 is distorted into a V-shape.